Fabric wipers used in clean room applications require low particle generation when flexed in air and when washed in water. In addition, the wipers must exhibit a high absorbency rate and capacity. However, particle and absorbency properties for many fabrics are many times mutually exclusive of each other. For example, 100% polyester fabrics generate low particle counts but provide almost no absorbency. On the other hand, cotton fabrics exhibit high absorbency rates and capacity but generate unacceptably high particle counts.
Commercially available spunlaced woodpulp/polyester (55%/45%) fabrics have proved adequate in Class 100 cleanroom environments (i.e., no more than 100 particles/ft.sup.3 air). Although this fabric may be acceptable in Class 100 environments, it is not acceptable in Class 10 environments. Class 10 environments (i.e., no more than 10 particles/ft.sup.3 air) are more desirable for sensitive clean room applications.
Example III of U.S. Pat. No. 3,485,709 (Evans) discloses hydroentangling an acrylic/polyester web to produce a spunlaced fabric. The fabric is made using a laboratory table washer. The hydroentanglement process calls for imparting high energy water jets to the web to entangle the web and produce a spunlaced fabric. In FIG. 40 of a related patent (U.S. Pat. No. 3,485,706 (Evans)), a continuous commercial process is disclosed wherein the fabric is subsequently dewatered by one or more squeeze rollers. Unfortunately, the application of high impact energy and squeeze roll dewatering generates particle counts which are unacceptable for sensitive cleanroom wiper applications.
Clearly, what is needed is a fabric which provides an adequate degree of absorbency but a low wet and dry particle count. In this regard, the applicants have found that spunlaced fabrics made of acrylic/polyester blends provide both low particle generation and good absorbency when processed under certain critical conditions. Specifically, the applicants have found that low water jet energy must be applied to the acrylic/polyester web in order to achieve an adequate balance of low wet and dry particle counts and good absorbency. Other objects and advantages of the present invention will become apparent to those skilled in the art upon reference to the attached drawings and to the detailed description of the invention which hereinafter follows.